Tuesday, 28 November 2017

That array_map quandary implemented in other languages

G'day:
A coupla days ago I bleated about array_map [having] a dumb implementation. I had what I thought was an obvious application for array_map in PHP, but it couldn't really accommodate me due to array_map not exposing the array's keys to the callback, and then messing up the keys in the mapped array if one passes array_map more than one array to process.

Note how the remapped object also contains the original key value. That was the sticking point. Go read the article for more detail and more whining.

OK so my expectations of PHP's array higher order functions are based on my experience with JS's and CFML's equivalents. Both of which receive the key as well as the value in all callbacks. I decided to see how other languages achieve the same end, and I'll pop the codee in here for shits 'n' giggles.

Also note that CFML doesn't have associative arrays, it has structs, so the keys are not ordered. This does not matter here.

JS

The next language I turned to was JS as that's the I'm next most familiar with. One thing that hadn't occurred to me is that whilst JS's Array implementation has a map method, we need to use an object here as the keys are values not indexes. And whilst I knew Objects didn't have a map method, I didn't know what the equivalent might be.

Well it turns out that there's no real option to use a map here, so I needed to do a reduce on the object's entries, Still: it's pretty terse and obvious:

TBH I think this is a misuse of an object to contain basically an associative array / struct, but so be it. It's the closest analogy to the PHP requirement. I was able to at least return it as a Map, which I think is better. I tried to have the incoming personData as a map, but the Map prototype's equivalent of entries() used above is unhelpful in that it returns an Iterator, and the prototype for Iterator is a bit spartan.

I think it's slightly clumsy I need to access the entries value via array notation instead of some sort of name, but this is minor.

As with all my code, I welcome people showing me how I should actually be doing this. Post a comment. I'm looking at you Ryan Guill ;-)

Java

Next up was Java. Holy fuck what a morass of boilterplate nonsense I needed to perform this simple operation in Java. Deep breath...

Most of that lot seems to be just messing around telling Java what types everything are. Bleah.

The interesting bit - my grasp of which is tenuous - is the Collectors.toMap. I have to admit I derived that from reading various Stack Overflow articles. But I got it working, and I know the general approach now, so that's good.

I wasn't too sure about all that block nonsense when I first started looking at Ruby, but I quite like it now. It's easy to read.

Python

My Python skills don't extend much beyond printing G'day World on the screen, but it was surprisingly easy to google-up how to do this. And I finally got to see what Python folk are on about with this "comprehensions" stuff, which I think is quite cool.

And now that I am all about Clean Code, I kinda get the "whitespace as indentation" thing too. It's clear enough if yer code is clean in the first place.

The output of this is identical to the Groovy one.

Only one more then I'll stop.

Clojure

I can only barely do G'day World in Clojure, so this took me a while to work out. I also find the Clojure docs to be pretty impentrable. I'm sure they're great if one already knows what one is doing, but I found them pretty inaccessible from the perspective of a n00b. It's like if the PHP docs were solely the user-added stuff at the bottom of each docs page. Most blog articles I saw about Clojure were pretty much just direct regurgitation of the docs, without much value-add, if I'm to be honest.

The other thing with Clojure for me is that the code is so alien-looking to me that I can't work out how to indent stuff to make the code clearer. All the examples I've seen don't seem very clear, and the indentation doesn't help either, I think. I guess with more practise it would come to me.

It seems pretty powerful though, cos there's mot much code there to achieve the desired end-goal.

This was before I did the Clojure one, and I'd slot that in afer CFML and before JS, making the list:

Python

Ruby

Groovy

CFML

Clojure

JS

PHP

Java

Python's code looks nice and it was easy to find out what to do. Same with Ruby, just not quite so much. And, really same with Groovy. I could order those three any way. I think Python tips the scales slightly with the comprehensions.

CFML came out suprisingly well in this, as it's a bloody easy exercise to achieve with it.

Clojure's fine, just a pain in the arse to understand what's going on, and the code looks a mess to me. But it does a lot in little space.

JS was disappointing because it wasn't nearly so easy as I expected it to be.

Hopefully he's still up for this, and I'll add it to the list so we can have a look at that code too.

Like I said before, if you know a better or more interesting way to do this in any of the languages above, or any other languages, make a comment and post a link to a Gist (just don't put the code inline in the comment please; it will not render at all well).

I might have another one of these exercises to do soon with another puzzle a friend of mine had to recently endure in a job-interview-related coding test. We'll see.

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About

I've been a web developer since 2001. I have spent 13yrs as a CFML developer, and until Sept 2014, that was the main subject matter here. I've now been re-tasked as a PHP developer, so learning PHP will become the focus of this blog. But I also mess around with other languages too.

I tend to be a bit "forthright" in my opinions, I am indelicate, and I tend to swear too much. This will come out occasionally here: I make no apology for it.

Everything said here is my own opinion. Feel free to disagree with me :-)